/* SPDX-License-Identifier: GPL-2.0 */
/*
 * Filesystem access notification for Linux
 *
 *  Copyright (C) 2008 Red Hat, Inc., Eric Paris <eparis@redhat.com>
 */

#ifndef __LINUX_FSNOTIFY_BACKEND_H
#define __LINUX_FSNOTIFY_BACKEND_H

#ifdef __KERNEL__

#include <linux/idr.h> /* inotify uses this */
#include <linux/fs.h> /* struct inode */
#include <linux/list.h>
#include <linux/path.h> /* struct path */
#include <linux/spinlock.h>
#include <linux/types.h>
#include <linux/atomic.h>
#include <linux/user_namespace.h>
#include <linux/refcount.h>

/*
 * IN_* from inotfy.h lines up EXACTLY with FS_*, this is so we can easily
 * convert between them.  dnotify only needs conversion at watch creation
 * so no perf loss there.  fanotify isn't defined yet, so it can use the
 * wholes if it needs more events.
 */
#define FS_ACCESS               0x00000001      /* File was accessed */
#define FS_MODIFY               0x00000002      /* File was modified */
#define FS_ATTRIB               0x00000004      /* Metadata changed */
#define FS_CLOSE_WRITE          0x00000008      /* Writtable file was closed */
#define FS_CLOSE_NOWRITE        0x00000010      /* Unwrittable file closed */
#define FS_OPEN                 0x00000020      /* File was opened */
#define FS_MOVED_FROM           0x00000040      /* File was moved from X */
#define FS_MOVED_TO             0x00000080      /* File was moved to Y */
#define FS_CREATE               0x00000100      /* Subfile was created */
#define FS_DELETE               0x00000200      /* Subfile was deleted */
#define FS_DELETE_SELF          0x00000400      /* Self was deleted */
#define FS_MOVE_SELF            0x00000800      /* Self was moved */
#define FS_OPEN_EXEC            0x00001000      /* File was opened for exec */

#define FS_UNMOUNT              0x00002000      /* inode on umount fs */
#define FS_Q_OVERFLOW           0x00004000      /* Event queued overflowed */
#define FS_IN_IGNORED           0x00008000      /* last inotify event here */

#define FS_OPEN_PERM            0x00010000      /* open event in an permission hook */
#define FS_ACCESS_PERM          0x00020000      /* access event in a permissions hook */
#define FS_OPEN_EXEC_PERM       0x00040000      /* open/exec event in a permission hook */
#define FS_DIR_MODIFY           0x00080000      /* Directory entry was modified */

#define FS_EXCL_UNLINK          0x04000000      /* do not send events if object is unlinked */
/* This inode cares about things that happen to its children.  Always set for
 * dnotify and inotify. */
#define FS_EVENT_ON_CHILD       0x08000000

#define FS_DN_RENAME            0x10000000      /* file renamed */
#define FS_DN_MULTISHOT         0x20000000      /* dnotify multishot */
#define FS_ISDIR                0x40000000      /* event occurred against dir */
#define FS_IN_ONESHOT           0x80000000      /* only send event once */

#define FS_MOVE                 (FS_MOVED_FROM | FS_MOVED_TO)

/*
 * Directory entry modification events - reported only to directory
 * where entry is modified and not to a watching parent.
 * The watching parent may get an FS_ATTRIB|FS_EVENT_ON_CHILD event
 * when a directory entry inside a child subdir changes.
 */
#define ALL_FSNOTIFY_DIRENT_EVENTS      (FS_CREATE | FS_DELETE | FS_MOVE | \
                                         FS_DIR_MODIFY)

#define ALL_FSNOTIFY_PERM_EVENTS (FS_OPEN_PERM | FS_ACCESS_PERM | \
                                  FS_OPEN_EXEC_PERM)

/*
 * This is a list of all events that may get sent to a parent based on fs event
 * happening to inodes inside that directory.
 */
#define FS_EVENTS_POSS_ON_CHILD   (ALL_FSNOTIFY_PERM_EVENTS | \
                                   FS_ACCESS | FS_MODIFY | FS_ATTRIB | \
                                   FS_CLOSE_WRITE | FS_CLOSE_NOWRITE | \
                                   FS_OPEN | FS_OPEN_EXEC)

/* Events that can be reported to backends */
#define ALL_FSNOTIFY_EVENTS (ALL_FSNOTIFY_DIRENT_EVENTS | \
                             FS_EVENTS_POSS_ON_CHILD | \
                             FS_DELETE_SELF | FS_MOVE_SELF | FS_DN_RENAME | \
                             FS_UNMOUNT | FS_Q_OVERFLOW | FS_IN_IGNORED)

/* Extra flags that may be reported with event or control handling of events */
#define ALL_FSNOTIFY_FLAGS  (FS_EXCL_UNLINK | FS_ISDIR | FS_IN_ONESHOT | \
                             FS_DN_MULTISHOT | FS_EVENT_ON_CHILD)

#define ALL_FSNOTIFY_BITS   (ALL_FSNOTIFY_EVENTS | ALL_FSNOTIFY_FLAGS)

struct fsnotify_group;
struct fsnotify_event;
struct fsnotify_mark;
struct fsnotify_event_private_data;
struct fsnotify_fname;
struct fsnotify_iter_info;

struct mem_cgroup;

/*
 * Each group much define these ops.  The fsnotify infrastructure will call
 * these operations for each relevant group.
 *
 * handle_event - main call for a group to handle an fs event
 * free_group_priv - called when a group refcnt hits 0 to clean up the private union
 * freeing_mark - called when a mark is being destroyed for some reason.  The group
 *              MUST be holding a reference on each mark and that reference must be
 *              dropped in this function.  inotify uses this function to send
 *              userspace messages that marks have been removed.
 */
struct fsnotify_ops {
        int (*handle_event)(struct fsnotify_group *group,
                            struct inode *inode,
                            u32 mask, const void *data, int data_type,
                            const struct qstr *file_name, u32 cookie,
                            struct fsnotify_iter_info *iter_info);
        void (*free_group_priv)(struct fsnotify_group *group);
        void (*freeing_mark)(struct fsnotify_mark *mark, struct fsnotify_group *group);
        void (*free_event)(struct fsnotify_event *event);
        /* called on final put+free to free memory */
        void (*free_mark)(struct fsnotify_mark *mark);
};

/*
 * all of the information about the original object we want to now send to
 * a group.  If you want to carry more info from the accessing task to the
 * listener this structure is where you need to be adding fields.
 */
struct fsnotify_event {
        struct list_head list;
        unsigned long objectid; /* identifier for queue merges */
};

/*
 * A group is a "thing" that wants to receive notification about filesystem
 * events.  The mask holds the subset of event types this group cares about.
 * refcnt on a group is up to the implementor and at any moment if it goes 0
 * everything will be cleaned up.
 */
struct fsnotify_group {
        const struct fsnotify_ops *ops; /* how this group handles things */

        /*
         * How the refcnt is used is up to each group.  When the refcnt hits 0
         * fsnotify will clean up all of the resources associated with this group.
         * As an example, the dnotify group will always have a refcnt=1 and that
         * will never change.  Inotify, on the other hand, has a group per
         * inotify_init() and the refcnt will hit 0 only when that fd has been
         * closed.
         */
        refcount_t refcnt;              /* things with interest in this group */

        /* needed to send notification to userspace */
        spinlock_t notification_lock;           /* protect the notification_list */
        struct list_head notification_list;     /* list of event_holder this group needs to send to userspace */
        wait_queue_head_t notification_waitq;   /* read() on the notification file blocks on this waitq */
        unsigned int q_len;                     /* events on the queue */
        unsigned int max_events;                /* maximum events allowed on the list */
        /*
         * Valid fsnotify group priorities.  Events are send in order from highest
         * priority to lowest priority.  We default to the lowest priority.
         */
        #define FS_PRIO_0       0 /* normal notifiers, no permissions */
        #define FS_PRIO_1       1 /* fanotify content based access control */
        #define FS_PRIO_2       2 /* fanotify pre-content access */
        unsigned int priority;
        bool shutdown;          /* group is being shut down, don't queue more events */

        /* stores all fastpath marks assoc with this group so they can be cleaned on unregister */
        struct mutex mark_mutex;        /* protect marks_list */
        atomic_t num_marks;             /* 1 for each mark and 1 for not being
                                         * past the point of no return when freeing
                                         * a group */
        atomic_t user_waits;            /* Number of tasks waiting for user
                                         * response */
        struct list_head marks_list;    /* all inode marks for this group */

        struct fasync_struct *fsn_fa;    /* async notification */

        struct fsnotify_event *overflow_event;  /* Event we queue when the
                                                 * notification list is too
                                                 * full */

        struct mem_cgroup *memcg;       /* memcg to charge allocations */

        /* groups can define private fields here or use the void *private */
        union {
                void *private;
#ifdef CONFIG_INOTIFY_USER
                struct inotify_group_private_data {
                        spinlock_t      idr_lock;
                        struct idr      idr;
                        struct ucounts *ucounts;
                } inotify_data;
#endif
#ifdef CONFIG_FANOTIFY
                struct fanotify_group_private_data {
                        /* allows a group to block waiting for a userspace response */
                        struct list_head access_list;
                        wait_queue_head_t access_waitq;
                        int flags;           /* flags from fanotify_init() */
                        int f_flags; /* event_f_flags from fanotify_init() */
                        unsigned int max_marks;
                        struct user_struct *user;
                } fanotify_data;
#endif /* CONFIG_FANOTIFY */
        };
};

/* When calling fsnotify tell it if the data is a path or inode */
enum fsnotify_data_type {
        FSNOTIFY_EVENT_NONE,
        FSNOTIFY_EVENT_PATH,
        FSNOTIFY_EVENT_INODE,
};

static inline const struct inode *fsnotify_data_inode(const void *data,
                                                      int data_type)
{
        switch (data_type) {
        case FSNOTIFY_EVENT_INODE:
                return data;
        case FSNOTIFY_EVENT_PATH:
                return d_inode(((const struct path *)data)->dentry);
        default:
                return NULL;
        }
}

static inline const struct path *fsnotify_data_path(const void *data,
                                                    int data_type)
{
        switch (data_type) {
        case FSNOTIFY_EVENT_PATH:
                return data;
        default:
                return NULL;
        }
}

enum fsnotify_obj_type {
        FSNOTIFY_OBJ_TYPE_INODE,
        FSNOTIFY_OBJ_TYPE_VFSMOUNT,
        FSNOTIFY_OBJ_TYPE_SB,
        FSNOTIFY_OBJ_TYPE_COUNT,
        FSNOTIFY_OBJ_TYPE_DETACHED = FSNOTIFY_OBJ_TYPE_COUNT
};

#define FSNOTIFY_OBJ_TYPE_INODE_FL      (1U << FSNOTIFY_OBJ_TYPE_INODE)
#define FSNOTIFY_OBJ_TYPE_VFSMOUNT_FL   (1U << FSNOTIFY_OBJ_TYPE_VFSMOUNT)
#define FSNOTIFY_OBJ_TYPE_SB_FL         (1U << FSNOTIFY_OBJ_TYPE_SB)
#define FSNOTIFY_OBJ_ALL_TYPES_MASK     ((1U << FSNOTIFY_OBJ_TYPE_COUNT) - 1)

static inline bool fsnotify_valid_obj_type(unsigned int type)
{
        return (type < FSNOTIFY_OBJ_TYPE_COUNT);
}

struct fsnotify_iter_info {
        struct fsnotify_mark *marks[FSNOTIFY_OBJ_TYPE_COUNT];
        unsigned int report_mask;
        int srcu_idx;
};

static inline bool fsnotify_iter_should_report_type(
                struct fsnotify_iter_info *iter_info, int type)
{
        return (iter_info->report_mask & (1U << type));
}

static inline void fsnotify_iter_set_report_type(
                struct fsnotify_iter_info *iter_info, int type)
{
        iter_info->report_mask |= (1U << type);
}

static inline void fsnotify_iter_set_report_type_mark(
                struct fsnotify_iter_info *iter_info, int type,
                struct fsnotify_mark *mark)
{
        iter_info->marks[type] = mark;
        iter_info->report_mask |= (1U << type);
}

#define FSNOTIFY_ITER_FUNCS(name, NAME) \
static inline struct fsnotify_mark *fsnotify_iter_##name##_mark( \
                struct fsnotify_iter_info *iter_info) \
{ \
        return (iter_info->report_mask & FSNOTIFY_OBJ_TYPE_##NAME##_FL) ? \
                iter_info->marks[FSNOTIFY_OBJ_TYPE_##NAME] : NULL; \
}

FSNOTIFY_ITER_FUNCS(inode, INODE)
FSNOTIFY_ITER_FUNCS(vfsmount, VFSMOUNT)
FSNOTIFY_ITER_FUNCS(sb, SB)

#define fsnotify_foreach_obj_type(type) \
        for (type = 0; type < FSNOTIFY_OBJ_TYPE_COUNT; type++)

/*
 * fsnotify_connp_t is what we embed in objects which connector can be attached
 * to. fsnotify_connp_t * is how we refer from connector back to object.
 */
struct fsnotify_mark_connector;
typedef struct fsnotify_mark_connector __rcu *fsnotify_connp_t;

/*
 * Inode/vfsmount/sb point to this structure which tracks all marks attached to
 * the inode/vfsmount/sb. The reference to inode/vfsmount/sb is held by this
 * structure. We destroy this structure when there are no more marks attached
 * to it. The structure is protected by fsnotify_mark_srcu.
 */
struct fsnotify_mark_connector {
        spinlock_t lock;
        unsigned short type;    /* Type of object [lock] */
#define FSNOTIFY_CONN_FLAG_HAS_FSID     0x01
        unsigned short flags;   /* flags [lock] */
        __kernel_fsid_t fsid;   /* fsid of filesystem containing object */
        union {
                /* Object pointer [lock] */
                fsnotify_connp_t *obj;
                /* Used listing heads to free after srcu period expires */
                struct fsnotify_mark_connector *destroy_next;
        };
        struct hlist_head list;
};

/*
 * A mark is simply an object attached to an in core inode which allows an
 * fsnotify listener to indicate they are either no longer interested in events
 * of a type matching mask or only interested in those events.
 *
 * These are flushed when an inode is evicted from core and may be flushed
 * when the inode is modified (as seen by fsnotify_access).  Some fsnotify
 * users (such as dnotify) will flush these when the open fd is closed and not
 * at inode eviction or modification.
 *
 * Text in brackets is showing the lock(s) protecting modifications of a
 * particular entry. obj_lock means either inode->i_lock or
 * mnt->mnt_root->d_lock depending on the mark type.
 */
struct fsnotify_mark {
        /* Mask this mark is for [mark->lock, group->mark_mutex] */
        __u32 mask;
        /* We hold one for presence in g_list. Also one ref for each 'thing'
         * in kernel that found and may be using this mark. */
        refcount_t refcnt;
        /* Group this mark is for. Set on mark creation, stable until last ref
         * is dropped */
        struct fsnotify_group *group;
        /* List of marks by group->marks_list. Also reused for queueing
         * mark into destroy_list when it's waiting for the end of SRCU period
         * before it can be freed. [group->mark_mutex] */
        struct list_head g_list;
        /* Protects inode / mnt pointers, flags, masks */
        spinlock_t lock;
        /* List of marks for inode / vfsmount [connector->lock, mark ref] */
        struct hlist_node obj_list;
        /* Head of list of marks for an object [mark ref] */
        struct fsnotify_mark_connector *connector;
        /* Events types to ignore [mark->lock, group->mark_mutex] */
        __u32 ignored_mask;
#define FSNOTIFY_MARK_FLAG_IGNORED_SURV_MODIFY  0x01
#define FSNOTIFY_MARK_FLAG_ALIVE                0x02
#define FSNOTIFY_MARK_FLAG_ATTACHED             0x04
        unsigned int flags;             /* flags [mark->lock] */
};

#ifdef CONFIG_FSNOTIFY

/* called from the vfs helpers */

/* main fsnotify call to send events */
extern int fsnotify(struct inode *to_tell, __u32 mask, const void *data,
                    int data_type, const struct qstr *name, u32 cookie);
extern int fsnotify_parent(struct dentry *dentry, __u32 mask, const void *data,
                           int data_type);
extern void __fsnotify_inode_delete(struct inode *inode);
extern void __fsnotify_vfsmount_delete(struct vfsmount *mnt);
extern void fsnotify_sb_delete(struct super_block *sb);
extern u32 fsnotify_get_cookie(void);

static inline int fsnotify_inode_watches_children(struct inode *inode)
{
        /* FS_EVENT_ON_CHILD is set if the inode may care */
        if (!(inode->i_fsnotify_mask & FS_EVENT_ON_CHILD))
                return 0;
        /* this inode might care about child events, does it care about the
         * specific set of events that can happen on a child? */
        return inode->i_fsnotify_mask & FS_EVENTS_POSS_ON_CHILD;
}

/*
 * Update the dentry with a flag indicating the interest of its parent to receive
 * filesystem events when those events happens to this dentry->d_inode.
 */
static inline void fsnotify_update_flags(struct dentry *dentry)
{
        assert_spin_locked(&dentry->d_lock);

        /*
         * Serialisation of setting PARENT_WATCHED on the dentries is provided
         * by d_lock. If inotify_inode_watched changes after we have taken
         * d_lock, the following __fsnotify_update_child_dentry_flags call will
         * find our entry, so it will spin until we complete here, and update
         * us with the new state.
         */
        if (fsnotify_inode_watches_children(dentry->d_parent->d_inode))
                dentry->d_flags |= DCACHE_FSNOTIFY_PARENT_WATCHED;
        else
                dentry->d_flags &= ~DCACHE_FSNOTIFY_PARENT_WATCHED;
}

/* called from fsnotify listeners, such as fanotify or dnotify */

/* create a new group */
extern struct fsnotify_group *fsnotify_alloc_group(const struct fsnotify_ops *ops);
/* get reference to a group */
extern void fsnotify_get_group(struct fsnotify_group *group);
/* drop reference on a group from fsnotify_alloc_group */
extern void fsnotify_put_group(struct fsnotify_group *group);
/* group destruction begins, stop queuing new events */
extern void fsnotify_group_stop_queueing(struct fsnotify_group *group);
/* destroy group */
extern void fsnotify_destroy_group(struct fsnotify_group *group);
/* fasync handler function */
extern int fsnotify_fasync(int fd, struct file *file, int on);
/* Free event from memory */
extern void fsnotify_destroy_event(struct fsnotify_group *group,
                                   struct fsnotify_event *event);
/* attach the event to the group notification queue */
extern int fsnotify_add_event(struct fsnotify_group *group,
                              struct fsnotify_event *event,
                              int (*merge)(struct list_head *,
                                           struct fsnotify_event *));
/* Queue overflow event to a notification group */
static inline void fsnotify_queue_overflow(struct fsnotify_group *group)
{
        fsnotify_add_event(group, group->overflow_event, NULL);
}

/* true if the group notification queue is empty */
extern bool fsnotify_notify_queue_is_empty(struct fsnotify_group *group);
/* return, but do not dequeue the first event on the notification queue */
extern struct fsnotify_event *fsnotify_peek_first_event(struct fsnotify_group *group);
/* return AND dequeue the first event on the notification queue */
extern struct fsnotify_event *fsnotify_remove_first_event(struct fsnotify_group *group);
/* Remove event queued in the notification list */
extern void fsnotify_remove_queued_event(struct fsnotify_group *group,
                                         struct fsnotify_event *event);

/* functions used to manipulate the marks attached to inodes */

/* Get mask of events for a list of marks */
extern __u32 fsnotify_conn_mask(struct fsnotify_mark_connector *conn);
/* Calculate mask of events for a list of marks */
extern void fsnotify_recalc_mask(struct fsnotify_mark_connector *conn);
extern void fsnotify_init_mark(struct fsnotify_mark *mark,
                               struct fsnotify_group *group);
/* Find mark belonging to given group in the list of marks */
extern struct fsnotify_mark *fsnotify_find_mark(fsnotify_connp_t *connp,
                                                struct fsnotify_group *group);
/* Get cached fsid of filesystem containing object */
extern int fsnotify_get_conn_fsid(const struct fsnotify_mark_connector *conn,
                                  __kernel_fsid_t *fsid);
/* attach the mark to the object */
extern int fsnotify_add_mark(struct fsnotify_mark *mark,
                             fsnotify_connp_t *connp, unsigned int type,
                             int allow_dups, __kernel_fsid_t *fsid);
extern int fsnotify_add_mark_locked(struct fsnotify_mark *mark,
                                    fsnotify_connp_t *connp,
                                    unsigned int type, int allow_dups,
                                    __kernel_fsid_t *fsid);

/* attach the mark to the inode */
static inline int fsnotify_add_inode_mark(struct fsnotify_mark *mark,
                                          struct inode *inode,
                                          int allow_dups)
{
        return fsnotify_add_mark(mark, &inode->i_fsnotify_marks,
                                 FSNOTIFY_OBJ_TYPE_INODE, allow_dups, NULL);
}
static inline int fsnotify_add_inode_mark_locked(struct fsnotify_mark *mark,
                                                 struct inode *inode,
                                                 int allow_dups)
{
        return fsnotify_add_mark_locked(mark, &inode->i_fsnotify_marks,
                                        FSNOTIFY_OBJ_TYPE_INODE, allow_dups,
                                        NULL);
}

/* given a group and a mark, flag mark to be freed when all references are dropped */
extern void fsnotify_destroy_mark(struct fsnotify_mark *mark,
                                  struct fsnotify_group *group);
/* detach mark from inode / mount list, group list, drop inode reference */
extern void fsnotify_detach_mark(struct fsnotify_mark *mark);
/* free mark */
extern void fsnotify_free_mark(struct fsnotify_mark *mark);
/* Wait until all marks queued for destruction are destroyed */
extern void fsnotify_wait_marks_destroyed(void);
/* run all the marks in a group, and clear all of the marks attached to given object type */
extern void fsnotify_clear_marks_by_group(struct fsnotify_group *group, unsigned int type);
/* run all the marks in a group, and clear all of the vfsmount marks */
static inline void fsnotify_clear_vfsmount_marks_by_group(struct fsnotify_group *group)
{
        fsnotify_clear_marks_by_group(group, FSNOTIFY_OBJ_TYPE_VFSMOUNT_FL);
}
/* run all the marks in a group, and clear all of the inode marks */
static inline void fsnotify_clear_inode_marks_by_group(struct fsnotify_group *group)
{
        fsnotify_clear_marks_by_group(group, FSNOTIFY_OBJ_TYPE_INODE_FL);
}
/* run all the marks in a group, and clear all of the sn marks */
static inline void fsnotify_clear_sb_marks_by_group(struct fsnotify_group *group)
{
        fsnotify_clear_marks_by_group(group, FSNOTIFY_OBJ_TYPE_SB_FL);
}
extern void fsnotify_get_mark(struct fsnotify_mark *mark);
extern void fsnotify_put_mark(struct fsnotify_mark *mark);
extern void fsnotify_finish_user_wait(struct fsnotify_iter_info *iter_info);
extern bool fsnotify_prepare_user_wait(struct fsnotify_iter_info *iter_info);

static inline void fsnotify_init_event(struct fsnotify_event *event,
                                       unsigned long objectid)
{
        INIT_LIST_HEAD(&event->list);
        event->objectid = objectid;
}

#else

static inline int fsnotify(struct inode *to_tell, __u32 mask, const void *data,
                           int data_type, const struct qstr *name, u32 cookie)
{
        return 0;
}

static inline int fsnotify_parent(struct dentry *dentry, __u32 mask,
                                  const void *data, int data_type)
{
        return 0;
}

static inline void __fsnotify_inode_delete(struct inode *inode)
{}

static inline void __fsnotify_vfsmount_delete(struct vfsmount *mnt)
{}

static inline void fsnotify_sb_delete(struct super_block *sb)
{}

static inline void fsnotify_update_flags(struct dentry *dentry)
{}

static inline u32 fsnotify_get_cookie(void)
{
        return 0;
}

static inline void fsnotify_unmount_inodes(struct super_block *sb)
{}

#endif  /* CONFIG_FSNOTIFY */

#endif  /* __KERNEL __ */

#endif  /* __LINUX_FSNOTIFY_BACKEND_H */